Since I received no reply to this, I figured it out myself. First input is the coaxial, second is the component, third is the composite, and fourth is the S-video. The problem is that the 3rd and 4th inputs share the audio. So I plugged in the audio for the 3rd into the right channel and the audio for the 4th into the left channel. If I only turn on the receiver/cable box of the device I want to use, I can have audio from the composite as well as the S-video inputs. Works nicely, since I don't care about stereo on my iPhone.